Diester of 3,5,3&#39;,5&#39;-tetrabromo-bisphenol A with halogenated aromatic carboxylic acid

ABSTRACT

A novel diester compound of the formula (I): ##STR1## wherein each of R 1  and R 2  represents a group of the formula (II): ##STR2## wherein X is bromine atom; Y at least one group selected from the group consisting of alkyl groups having 1 to 4 carbon atoms, alkoxy groups having 1 to 4 carbon atoms, hydroxyl group and primary, secondary or tertiary amino groups; p an integer of 0 to 4; q an integer of 1 to 4; r an integer 1 to 4 and (q+r) is equal to an integer of not more than 5, is found to be capable of imparting excellent flame-retardancy to various inflammable polymeric materials such as polystyrene, polyester, polyamide, polyphenylene oxide, etc. without deleterious effects on other physical properties of such polymeric materials.

This invention relates to novel bromine containing diester compoundswhich are particularly useful for imparting flame-retardancy to variouspolymeric materials.

A typical example of bromine containing flame-retardant additives knownin the art is deca-bromodiphenylether. This compound, however, is veryinferior in weathering resistance. As another example, there is alsoknown 3,5,3',5'-tetrabromo-bisphenol A, which will disadvantageouslylower heat distortion temperature of polymeric materials to a greatextent when incorporated therein.

British Pat. No. 1,281,937 discloses a compound of the formula: ##STR3##wherein R is an alkyl group having 1 to 3 carbon atoms. This compoundalso has the drawback to lower remarkably heat distortion temperature ofpolymeric materials to which said compound is added.

U.S. Pat. No. 3,846,469 discloses a compound of the formula: ##STR4##wherein m is an integer of 3 to 5. Such a compound can be added topolymeric materials for improvement of flame-retardancy only withdisadvantageous decrease in impact strength of polymeric materials.

Furthermore, there is reported a compound of the formula: ##STR5##wherein n is 1 or 2, in Journal of Chemical and Engineering Data, Vol.12, p. 252(1967). The compound is by far inferior in the effect ofimparting flame-retardancy to polymeric materials to the compound of thepresent invention. Accordingly, in order to obtain equal levels ofimprovement in flame-retardancy, it is required to add a large amount ofsuch a compound to inflammable polymeric materials, whereby otherproperties such as weathering resistance, heat distortion temperatureand impact strength, etc. of the resultant polymeric materials aregreatly impaired.

In accordance with the present invention, there is provided a noveldiester compound represented by the following formula (I): ##STR6##wherein R₁ and R₂, which may either be identical or different, representthe groups of the formula (II): ##STR7## wherein X is bromine atom; Y atleast one group selected from the group consisting of alkyl groupshaving 1 to 4 carbon atoms, alkoxy groups having 1 to 4 carbon atoms,hydroxyl group and primary, secondary or tertiary amino groups; p aninteger of 0 to 4; q an integer of 1 to 4; r an integer of 1 to 4; and(q+r) is equal to an integer of not more than 5.

In the above formula (II), the notation --(X)_(q) representscomprehensively bromine atoms in number of q substituted on the aromaticnucleus; while the notation --(Y)_(r) comprehensively at least onesubstituents in number of r, which may be identical or different,selected from the groups as enumerated above.

Typical examples of R₁ and R₂ may include 4-methyl-3-bromophenyl;4-methyl-3,5-dibromophenyl; 2-methyl-5-bromophenyl;2-methyl-3,5-dibromophenyl; 2-methoxy-3,5-dibromophenyl;2-methoxy-3-bromophenyl; 2-methoxy-3,5-dibromophenyl;4-methoxy-3,5-dibromophenyl; 2-hydroxy-3,5-dibromophenyl;4-hydroxy-3,5-dibromophenyl; 2-amino-3,5-dibromophenyl;4-amino-3,5-dibromophenyl; 4-dimethylamino-3,5-dibromophenyl;4-amino-3,5-dibromophenylmethyl; 2-hydroxy-3,5-dibromophenylmethyl; andthe like.

The compound of the present invention has excellent heat stability andweathering resistance as well as excellent effect of impartingflame-retardancy to inflammable polymeric materials and is also freefrom the drawbacks of lowering impact strength and heat distortiontemperature of polymeric materials when incorporated therein.

The compound of the present invention can be prepared according tovarious methods. For example, according to one method, it can beprepared by esterification of 3,5,3',5'-tetrabromo-bisphenol A with oneor two carboxylic acids having the groups (II) as mentioned above,(which may be the same or different), in a non-alcoholic solvent such asbenzene, toluene, tetrahydrofuran, ether or pyridine, using an acidcatalyst such as sulfuric acid, hydrogen chloride, an aromatic sulfonicacid derivative, p-toluenesulfonic acid, phosphorus oxychloride,polyphosphoric acid, boron trifluoride, phosphorus pentachloride, boricacid-sulfuric acid, boron trifluoride etherate, trifluoroacetic acid,dicyclohexyl carbodiimide, etc.

As an alternative method, a carboxylic acid having the groups asrepresented by the formula (II) can be first converted to an acid halideby reaction with a reagent such as phosphorus trichloride, phosphoruspentachloride, thionyl chloride, triphenylphosphine dibromide,triphenylphosphine-carbon tetrachloride, thionylchloride-dimethylformamide, thionyl chloride-pyridine (in the presenceof zinc chloride catalyst), thionyl chloride-iodine, phosphoruspentachloride-acetyl chloride, etc. in the absence of a solvent or in asolvent such as benzene, methylene chloride, chloroform,tetrahydrofuran, ether, etc. The resultant acid halide is then subjectedto esterification with 3,5,3',5'-tetrabromo-bisphenol A in the presenceof a base such as sodium hydroxide, potassium hydroxide, dimethylaniline, pyridine, sodium hydride, tetramethyl urea, and the like.

According to another method, a carboxylic acid anhydride having thegroups as represented by the formula (II) can be esterified with3,5,3',5'-tetrabromo-bisphenol A in the presence of a catalyst selectedfrom sulfuric acid, zinc chloride, chlorosulfonic acid, sodium acetate,sodium methylate, p-toluenesulfonic acid and pyridine.

Furthermore, there may also be employed a method in which a nitrilehaving the groups of the formula (II) is reacted with3,5,3',5'-tetrabromo-bisphenol A under anhydrous conditions in thepresence of an acid catalyst such as hydrogen chloride, hydrogenbromide, hydrogen iodide, sulfuric acid, p-toluenesulfonic acid, etc.

The polymeric materials to which flame-retardancy can be imparted by thecompound according to the present invention may be exemplified bypolystyrene (including rubber-modified high impact polystyrene), ASresin, ABS resin, polyphenylene oxide, polyester, polyamide,polyethylene, polypropylene, polyisoprene, polybutadiene, polyacrylate,polycarbonate, etc. Polymeric mixtures comprising two or more of thesepolymers in suitable blending ratios may also be available.

If desired, other halo-containing flame-retardants and/orphosphorus-containing flame-retardants may also be used in combinationwith the compound of the present invention. Furthermore, there may alsobe added one or more synergetic flame-retardants such as antimonytrioxide, zirconium silicate, zinc borate, titanium phosphate, redphosphorus, molybdenum oxide and others.

The effective amount of the present compound to be added for impartingflame-retardancy may depend on the extent of flame-retardancy requiredand the polymeric material to be applied. For example, for a polystyreneto be acceptable as V-O rate according to the UL-94 test method, it isnecessary to add 10 to 30 parts by weight of the compound of the presentinvention and 2 to 10 parts by weight of antimony trioxide per 100 partsby weight of polystyrene. For all of the resins as mentioned above,preferable compositions comprise 100 parts by weight of an inflammablepolymer, 5 to 40 parts by weight of a compound of the present inventionand 0 to 15 parts by weight of antimony trioxide. Furthermore, there mayalso be added other conventional additives together with the compound ofthe present invention, such as stabilizers, coloring agents, anti-staticagents, foaming agents, light stabilizers, fillers, etc.

The present invention is explained in further detail with reference tothe following Examples, by which the present invention is not limitedbut various modifications are possible within the spirit of theinvention.

EXAMPLE 1 Synthesis of di-(4-amino-3,5-dibromobenzoic acid)ester

In a flask equipped with a reflux condenser, 88.5 g (0.3 mole) of4-amino-3,5-dibromobenzoic acid and 68 g (0.33 mole) of phosphoruspentachloride were reacted under reflux for one hour. After removal ofphosphorus oxychloride under reduced pressure by means of an aspirator,the reaction product is subjected to vacuum distillation to obtain 69 gof 4-amino-3,5-dibromobenzoic acid chloride (yield: 73%).

While stirring a solution of 54.4 g (0.1 mole) of3,5,3',5'-tetrabromo-bisphenol A and 30 ml of pyridine in 300 ml oftetrahydrofuran at room temperature, 63 g (0.2 mole) of the above4-amino-3,5-dibromobenzoic acid chloride was slowly added dropwise,whereby white crystals were formed immediately. After the dropwiseaddition, stirring was continued for additional three hours at roomtemperature to complete the reaction, followed by evaporation oftetrahydrofuran. The residual crystals were dissolved in chloroform andthe resultant solution was washed twice with ammonia water and threetimes with water. Thereafter, the washed solution was dried overanhydrous sodium sulfate, followed by removal of the solvent. Theresultant crystals were recrystallized from ethanol/benzene (1:4) togive 93 g of white crystals (yield: 85%).

Elemental analysis: C₂₉ H₁₈ N₂ O₄ Br₈ ; Calculated: C, 31.69; H, 1.64;Br, 58.29; Found: C, 31.72; H, 1.61; Br, 58.18.

Infra-red spectrum: Absorptions of ester found at 1760 cm⁻¹ and 1240cm⁻¹.

EXAMPLE 2 Synthesis of di-(2-hydroxy-3,5-dibromobenzoic acid)ester

Example 1 was repeated, except that 89 g (0.3 mole) of2-hydroxy-3,5-dibromobenzoic acid was used in place of4-amino-3,5-dibromobenzoic acid, to obtain 102 g ofdi-(2-hydroxy-3,5-dibromobenzoic acid)ester (yield: 93%).

Elemental analysis: C₂₉ H₁₆ Br₈ O₆ ; Calculated: C, 31.64; H, 1.45; Br,58.18; Found: C, 31.57; H, 1.49; Br, 58.21.

EXAMPLE 3 Synthesis of di-(4-methoxy-3,5-dibromobenzoic acid)ester

Using 93 g (0.3 mole) of 4-methoxy-3,5-dibromobenzoic acid in place of4-amino-3,5-dibromobenzoic acid, the reaction was carried out under thesame conditions as in Example 1 to obtain 103 g ofdi-(4-methoxy-3,5-dibromobenzoic acid)ester as white powders (yield:91%).

Elemental analysis: C₃₁ H₂₀ O₆ Br₈ ; Calculated: C, 32.98; H, 1.77; Br,56.74; Found: C, 32.95; H, 1.78; Br, 56.69.

Infra-red spectrum: Absorptions of ester found at 1760 cm⁻¹ and 1240cm⁻¹

EXAMPLE 4 Synthesis of diester with 4-methyl-2,6-dibromobenzoic acid

By carrying the reaction in the same manner as in Example 1 except that88 g (0.3 mole) of 4-methyl-2,6-dibromobenzoic acid was used in place of3,5-dibromobenzoic acid, there was prepared 95 g ofdi-(4-methyl-2,6-dibromobenzoic acid)ester (yield: 87%).

Elemental analysis: C₃₁ H₂₀ O₄ Br₈ ; Calculated: C, 33.94; H, 1.82; Br,58.39; Found: C, 33.91; H, 1.85; Br, 58.41.

Infra-red spectrum: Absorptions of ester found at 1760 cm⁻¹ and 1240cm⁻¹

EXAMPLE 5 Preparation of flame-retardant polystyrene resin composition

A mixture comprising 100 parts by weight of a high impact polystyrene(Styron 475 D, produced by Asahi-Dow Limited, Japan), 20 parts by weightof the di-(4-amino-3,5-dibromobenzoic acid)ester as prepared in Example1 and 5 parts by weight of antimony trioxide was prepared in a drumblender and extruded at 250° C. into pellets by an extruder having aDulmage type screw. Using an injection molding machine, these pelletswere molded at 220° C. into test pieces with thickness of 1/8". Therewas substantially no discoloration of the resin in the test piece evenby molding after permitting the resin to be molded to reside in thecylinder of the molding machine for 10 minutes, indicating good heatstability. When burning test was conducted according to the test methodUL-94, the test samples were found to be self-extinguishing with V-Orate. The test samples were also found to have an Izod impact strengthwith notch of 7.7 Kg·cm/cm (according to JIS-K6871), which impactstrength was retained at as high as 5.8 Kg·cm/cm when measured afterexposure of the sample to a Sunshine Weather-meter for 400 hours. Thesamples were also found to have a Vicat softening point (ASTM-D 1525) of104° C.

EXAMPLE 6 Preparation of flame-retardant polyphenyleneoxide resincomposition

One hundred parts by weight of a polyphenyleneoxide resin (Xyron 500 H:produced by Asahi-Dow Limited), 20 parts by weight of thedi-(4-amino-3,5-dibromobenzoic acid)ester as prepared in Example 1 and 5parts by weight of antimony trioxide were blended in a drum blender andextruded at 250° C. into pellets by an extruder having a Dulmage typescrew. Then, the pellets were injection molded into test pieces withthickness of 1/8". Burning test was conducted according to the testmethod UL-94, whereby the samples were found to be self-extinguishingwith V-O rate.

EXAMPLE 7 Preparation of flame-retardant polybutylene terephthalateresin composition

One hundred parts by weight of a polybutylene terephthalate resin (PBT1401 of a Toray's product), 20 parts by weight of thedi-(4-amino-3,5-dibromobenzoic acid)ester as prepared in Example 1 and 7parts by weight of antimony trioxide were blended in a drum blender andextruded (at 250° C.) into pellets by an extruder having a Dulmage typescrew. Then, the pellets were injection molded into test pieces withthickness of 1/8". Burning test was conducted according to the testmethod UL-94, whereby the samples were found to be self-extinguishingwith V-O rate.

EXAMPLE 8 Preparation of flame-retardant polyamide composition

The same procedure as in Example 7 ws repeated except that 100 parts byweight of nylon 6 (Toray's Amilan 1017) were used in place of thepolybutylene terephthalate resin and that the amount of thedi-(4-amino-3,5-dibromobenzoic acid was changed to 15 parts by weight.The result of the burning test was the same as in Example 7.

EXAMPLES 9-11

Various flame-retardant polystyrene compositions were prepared accordingto the same procedure as in Example 5 except for using various diestersas prepared in Examples 2 to 4 for the compositions of Examples 9 to 11,respectively. The result of burning test conducted by the same method asin Example 5 for any of the samples prepared from these compositions wassimilar to that reported in Example 5.

What we claim is:
 1. A compound of the formula (I): ##STR8## wherein R₁and R₂, which may be identical or different, represent the groups of theformula (II): ##STR9## wherein X is bromine atom; Y at least one groupselected from the group consisting of alkoxy groups having 1 to 4 carbonatoms, hydroxyl groups and primary, secondary or tertiary amino groups;p an integer of 0 to 4; q an integer of 1 to 4; r an integer of 1 to 4;and (q+r) is equal to an integer of not more than
 5. 2. A compoundaccording to claim 1 where Y is a primary, secondary, or tertiary aminogroup.
 3. A compound according to claim 2 where Y is a primary aminogroup.
 4. A compound according to claim 3 where q is 1 to 2 and r is 1.5. A compound according to claim 4 where R₁ and R₂ are identical and are##STR10##
 6. A compound according to claim 1 where Y is alkoxy of 1 to 4carbon atoms.
 7. A compound according to claim 6 where q is 1 to 2 and ris
 1. 8. A compound according to claim 1 where Y is hydroxyl.
 9. Acompound according to claim 8 where q is 1 to 2 and r is
 1. 10. Apolymeric material improved in flame-retardancy, comprising:(a) at leastone inflammable polymer selected from the group consisting ofpolystyrene, acrylonitrilestyrene resin, acrylonitrile-butadiene-styreneresin, polyphenylene oxide, polyester, polyamide, polyethylene,polypropylene, polyisoprene, polybutadiene, polyacrylate andpolycarbonate; and (b) at least one compound of the formula (I):##STR11## wherein R₁ and R₂, which may be identical or different,represent the groups of the formula (II): ##STR12## wherein X is bromineatom; Y at least one group selected from the group consisting of, alkoxygroups having 1 to 4 carbon atoms, hydroxyl group and primary, secondaryor tertiary amino groups; p an integer of 0 to 4; q an integer of 1 to4; r an integer of 1 to 4; and (q+r) is equal to an integer of not morethan
 5. 11. A polymeric material according to claim 10, comprising 100parts by weight of the inflammable polymer (a), 5 to 40 parts by weightof the compound (b) and 0 to 15 parts by weight of antimony trioxide.12. A polymeric material according to claim 3, wherein the inflammablepolymer (a) is polystyrene.
 13. A polymeric material according to claim3, wherein the inflammable polymer (a) is polyphenyleneoxide.
 14. Apolymeric material according to claim 3, wherein the inflammable polymer(a) is polyester.
 15. A polymeric material according to claim 3, whereinthe inflammable polymer (a) is polyamide.
 16. A polymeric materialaccording to claim 3, wherein the inflammable polymer (a) ispolycarbonate.
 17. A polymer material according to claim 2 where Y is aprimary, secondary, or tertiary amino group.
 18. A polymer materialaccording to claim 17 where q is 1 to 2 and r is
 1. 19. A polymermaterial according to claim 18 where R₁ and R₂ are identical and are##STR13##
 20. A polymer material according to claim 2 where Y is alkoxyof 1 to 4 carbon atoms.
 21. A polymer material according to claim 20where q is 1 to 2 and r is
 1. 22. A polymer material according to claim2 where Y is hydroxyl.
 23. A polymer material according to claim 22where q is 1 to 2 and r is
 9. 24. A compound of the formula (1)##STR14## wherein R₁ and R₂, which may be identical or different,represent the groups of the formula (II) ##STR15## where X is bromineatom; Y is at least one group selected from the group consisting ofalkyl groups having 1 to 4 carbon atoms, alkoxy groups having 1 to 4carbon atoms, hydroxyl groups and primary, secondary or tertiary aminogroups; p an integer of 1 to 4; q an integer of 1 to 4; r an integer of1 to 4; and (q+r) is equal to an integer of not more than
 5. 25. Apolymeric material improved in flame-retardancy, comprising(a) at leastone inflammable polymer selected from the group consisting ofpolystyrene, acrylonitrile-styrene resin,acrylonitrile-butadiene-styrene resin, polyphenylene oxide, polyester,polyamide, polyethylene, polypropylene, polyisoprene, polybutadienepolyacrylate, and polycarbonate; and (b) at least one compound of theformula (I) ##STR16## wherein Rhd 1 and R₂, which may be identical ordifferent, represent the group of the formula (II) ##STR17## wherein Xis bromine atom, Y at least one group selected from the group consistingof alkyl groups having 1 to 4 carbon atoms, alkoxy groups having 1 to 4carbon atoms, hydroxyl group and primary, secondary or tertiary aminogroups; p an integer of 1 to 4; q an integer of 1 to 4, r an integer of1 to 4; and (q+r) is equal to an integer of not more than 5.